1. Field of the Invention
The present invention relates to a power device for visual care, and more particularly, to a power device having a homing sensor, a positive air pressure micro switch and a negative air pressure micro switch so as to provide proper air pressure.
2. Description of the Prior Art
A conventional air pressure assembly (10) incorporated with an air pipe (11) generates positive air pressure and negative air pressure to an eyeshade (not shown in the drawing) for visual care, which provides a pressure or suction effect for correcting vision or visual care.
The conventional air pressure assembly (10) comprises a motor (12) with a spindle (13) to drive a power screw (14). A screw seat (15) is screwed to the power screw (14) and coupled with a piston (16). A pneumatic cylinder (17) is fitted on the piston (16) and the screw seat (15). The pneumatic cylinder (17) has guide grooves (171, 172) corresponding to bearings (151, 152) of the screw seat (15) to ensure that the piston (16) slides thereon without rotation. When the motor (12) drives the spindle (13) and the power screw (14) to turn, the screw seat (15) and the piston (16) will be moved to reciprocate linearly, such that the piston (16) will generate positive/negative air pressure or suction which is sent to the eyeshade through the air pipe (11) for visual care.
However, the conventional air pressure assembly (10) has the following shortages. The conventional air pressure assembly (10) doesn't check position and return-to-zero. After a period of time, the positive/negative air pressure generated by the conventional air pressure assembly (10) may be too much or not enough. This will influence the effect of the visual care. Accordingly, the inventor of the present invention has devoted himself based on his many years of practical experiences to solve this problem.